Mechanical Engineering - PhD Internal Presentation of Ali Shojaeizoeram-FR

Event date(s): July 28, 2026
Time(s): 01:00 PM - 03:00 PM
Category: Fredericton
Location: Fredericton

This thesis investigates how the microstructure of LPBF-manufactured A205 aluminum alloy evolves in the as-built and heat-treated conditions, and how these changes affect its mechanical behavior under different loading conditions. The work focuses on understanding the combined influence of TiB2-assisted grain refinement, post-build heat treatment, and deformation conditions on the performance of this high-strength A1-Cu-based alloy. The thesis is presented in article format and brings together four related studies covering baseline microstructure and mechanical behavior, hot deformation, and high-strain-rate response. The results show that LPBF processing combined with TiB2 inoculation produces a fine equiaxed microstructure in the ultrafine-grained range, with weak texture and alloying-element enrichment along grain boundaries. This refined as-built structure strongly affects the later deformation behavior of the alloy. After T7 heat treatment, the microstructure changes considerably through uneven grain growth, the formation of strengthening precipitates such as θ and Ω, and the development of precipitation-free zones along grain boundaries. These changes significantly improve strength, but they also reduce ductility and  introduce local microstructural heterogeneity. Under hot deformation, both the as-built and eat-treated conditions exhibit temperature and strain-rate-dependent flow softening,  although the dominant mechanisms differ. In the as-built condition, the ultrafine-grained structure promotes dynamic recovery, dynamic recrystallization, and grain rotation-induced grain coalescence. In the heat-treated condition, precipitation strengthening increases the flow stress, but deformation is also influenced by PFZ-assisted softening and the gradual loss of precipitate effectiveness during continued loading. Under high-strain-rate loading, the as-built alloy deforms uniformly without visible adiabatic shear bands or cracking, with grain boundary sliding and dynamic recrystallization playing key roles in strain accommodation. In the heat-treated alloy, PFZs strongly influence local strain accumulation, dynamic recrystallization, and negative strain-rate sensitivity, while interactions between dislocations and Ω precipitates reduce the effectiveness of precipitation strengthening. Overall, this thesis establishes a clear link between processing, microstructure, and deformation behavior in LPBF A205 alloy and highlights the importance of grain refinement, PFZs, and precipitate stability in controlling performance across different loading conditions.This thesis investigates how the microstructure of LPBF-manufactured A205 aluminum alloy evolves in the as-built and heat-treated conditions, and how these changes affect its mechanical behavior under different loading conditions. The work focuses on understanding the combined influence of TiB2-assisted grain refinement, post-build heat treatment, and deformation conditions on the performance of this high-strength A1-Cu-based alloy. The thesis is presented in article format and brings together four related studies covering baseline microstructure and mechanical behavior, hot deformation, and high-strain-rate response. The results show that LPBF processing combined with TiB2 inoculation produces a fine equiaxed microstructure in the ultrafine-grained range, with weak texture and alloying-element enrichment along grain boundaries. This refined as-built structure strongly affects the later deformation behavior of the alloy. After T7 heat treatment, the microstructure changes considerably through uneven grain growth, the formation of strengthening precipitates such as θ and Ω, and the development of precipitation-free zones along grain boundaries. These changes significantly improve strength, but they also reduce ductility and  introduce local microstructural heterogeneity. Under hot deformation, both the as-built and eat-treated conditions exhibit temperature and strain-rate-dependent flow softening,  although the dominant mechanisms differ. In the as-built condition, the ultrafine-grained structure promotes dynamic recovery, dynamic recrystallization, and grain rotation-induced grain coalescence. In the heat-treated condition, precipitation strengthening increases the flow stress, but deformation is also influenced by PFZ-assisted softening and the gradual loss of precipitate effectiveness during continued loading. Under high-strain-rate loading, the as-built alloy deforms uniformly without visible adiabatic shear bands or cracking, with grain boundary sliding and dynamic recrystallization playing key roles in strain accommodation. In the heat-treated alloy, PFZs strongly influence local strain accumulation, dynamic recrystallization, and negative strain-rate sensitivity, while interactions between dislocations and Ω precipitates reduce the effectiveness of precipitation strengthening. Overall, this thesis establishes a clear link between processing, microstructure, and deformation behavior in LPBF A205 alloy and highlights the importance of grain refinement, PFZs, and precipitate stability in controlling performance across different loading conditions.

Building: https://teams.microsoft.com/meet/246998458858384?p=HndhAil9y3psaLvgIH